Delay action blasting cap



M y 1950 J. LORET 2,566,157

' DELAY ACTION BLASTING CAP Filed April 25, 1946 INVENTO R JACQUES LOR ET Patented May 2, 1950 UNITED STATES PATENT GF-FEQE DELAY ACTION BLASTIN G CAP Jacques Loret, Sevres, France, assignor to Etablissements Marcel Gaupillat, Paris, France, a

society of France Application April 25, 1946, Serial No. 664,796 InFrance November 29, 1945 5 Claims. 1

. in such manner as to permit of ensuring, by simultaneous operation of several blasting capshaving suitably chosen different delays, successive explosions atgiven intervals, as desired for instance in mining, quarrying and analogous operations.

The chief object .of my invention is to provide a. device of this kind which is better adapted to .meet the requirements of practice than those obtained for the same purpose up to the present time,especially.from the point of View of precision.

A preferred embodiment of my invention will be hereinafter described with reference to the accompanying drawing, given merely by way of example, and in which the only figure .is a diagrammatic sectional view of a blasting cap made ac- .cording to my invention.

It should first be reminded that, in existing devices of the kind in question, the connection between the ignition charge and the detonating charge is most generally obtained by means of a (fuse or .any other analogous body or device the combustion of which is produced by thefiring 1 of the ignition charge, this combustion corresponding to a variable time which constitutesthe delay provided before the firing of the detonating charge.

Therefore, indevices of this kind, the delay is the time of combustion of .a given intermediate body. But experience has taught that the pre ing charge for firing the latter, instead "of being ensured by the combustion of an intermediate vbody isensured by heat conductivity through at least one suitable medium.

The delay then corresponds to the time necessary for the propagation of heat through this medium.

Preferably, I provide means for obtaining a substantially constant value of the temperature 2 t1. produced by the combustion of the lgni-tlo charge, whereby the dela .R is determined, as accurately as possible by a formula such as the following one:

in which is is the temperature of the surrounding atmosphere, and K a coefficient which 'is variable according to the matter, the shape and the dimensions (cross section, length, etc.) of the intermediate medium through which the caloriesare propagated.

The blasting cap, considered as a whole, and

:apart from the means for interconnecting the two charges above mentioned. may 'be of any suitable conventional construction, For instance the ignition charge I is located atthe-base of- -a brass tube or the like 2, provided with a plug 3 through which pass the electric wires provided for firing the charge. The detonating charge H is provided at the other end of the tube, with an interval between charges 'I and II intended to contain the interconnecting means above referred to.

The charges may be made in any knownmanner, charge I consisting of a composition of mat- ;ter capable of giving 01f a great-amount of heat in a very short time, preferably with a minimum production of gases (although this condition is not absolutely necessary), whilst charge II is constituted by a knownexplosive.

The interconnecting means in question are for instance constituted by a rod, such asl, intended to transmit heat. This rod is therefore advantageously made of a metal which is a good conductor of heat. (coppen'brass, steel, etci). although other, materials may be utilized which are more or less .good heat conductors, according to the value of the delay R .to be obtained.

At the end of this rod that corresponds to the ignition charge, .means are providedfor ensuring .agood transmission of heat from said charge, to

said rod, said means including for instancefla kind of socket 5 carried by rod 4 (integral with said rod in the embodiment illustrated by the @drawing) and adapted to. contain the ignition I .charge' I. I

Thissocket, which is for instance secured on ,plug .3, can-be calculated to ,resist .the stresses-that .areip foduced whenthe charge is fired (due in particular to the disengagement of gases) in order to avoid any projection of hot gases or flames before the explosion of the detonating charge, so as to comply with the safety regulations provided in the mining industry.

If it is desired to have a temperature ii that remains substantially constant, I may provide means making use of a physical phenomenon tending to keep the temperature at a constant value during the combustion of the charge. For instance, I may utilize the latent heat of fusion of a suitable body.

Thus the thermic powder which constitutes said charge may be mixed with tin in powdery or any other suitable form, or any other body having a well defined melting point.

This body may be either distributed through the whole mass of the ignition charge or, on the contrary, concentrated at certain points, for instance at the bottom of socket 5, as shown at 6.

In this latter case, the layer 6 of tin and the matter of the ignition charge I are preferably arranged so as to penetrate each other by means of teeth such as 1 in order to ensure an intimate .contact between them. The temperature then reaches, at the time of combustion, the melting point of layer 6 and tends to keep at this value.

in the embodiment shown by the drawings, by the mass of air which surrounds this rod.

With an arrangement such as above described, when the firing of the ignition charge is obtained by passage of electric current through the filament, a certain amount of calories is produced by the combustion of this charge, and these calories tend to propagate themselves along rod 4. After a certain time, which depends upon the characteristics of said rod, a sufficiently high temperature is obtained at the end of this rod for causing fulminating element 8 to explode and to produce the explosion of the detonating charge.

- The transmission of heat through rod 4 can be calculated in an extremely accurate manner as a function of various factors which can be modified at will, to wit: 5o "a. The nature of the metal or other material of the other end at a dlstance from Sald detonating which this rod is made;

L b. The cross section area of this rod; c. Its shape; and

:1. Its length. I These various factors make it possible to determine the above mentioned coefficient k.

, the powder that is used for constituting the igni- 60 I can also vary the initial temperature h by suitably choosing the quality and. composition of tion charge.

It' is. therefore possible to obtain any desired series of blasting caps having time delays that differ from one another by extremely small Ina general manner, while I have, in the above wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

What I claim is:

l. A delay action blasting cap which comprises, in combination, an ignition charge, a detonating charge at a distance from said ignition charge, a piece of a heat conducting incombustible material extending between said two charges with one end in intimate contact with said ignition charge and the other end at a distance from said detonating charge, and a fulminating element carried by said last mentioned end of said piece and out of contact with said detonating charge.

2. A delay action blasting cap which comprises, in-combination, an ignition charge, a detonating charge at a distance from said ignition charge, a metal rod extending between said two charges with one end in intimate contact with said ignition charge and the other end at a distance from said detonating charge, and a fulminating element carried by said last mentioned end of said piece and out of contact with said detonating charge.

3. A blasting cap according to claim 2 further including a casing surrounding the space between said ignition and detonating charges, and a gaseous atmosphere in said space around said rod.

4. A delay action blasting cap which comprises, in combination, an ignition charge, a detonating charge at a distance from said ignition charge, a piece of a heat conducting incombustible material extending between said two charges with one end in intimate contact with said ignition charge and the other end at a distance from said detonating charge, a fulminating element carried by said last mentioned end of said piece and out of contact with said detonating charge, and means for keeping the temperature of said ignition charge at a constant value during combustion thereof.

5. A delay action blasting cap which comprises, in combination, an ignition charge, a detonating charge at a distance from said ignition charge, a piece of a heat conducting incombustible material extending between said two charges with one end in intimate contact with said ignition charge and charge, a fulminating element carried by said last mentioned end of said piece and out of contact with said detonating charge, and a body having a well defined melting point added to said ignition charge for keeping the temperature thereof at a constant value during its combustion. I Y I JACQUES LORET.

REFERENCES CITED The following references are of. record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,093,353 Geitmann Sept. 14, 1937 2,103,014 Palmieri Dec. 21, 1937 2,185,370 Burrows et a1 Jan. 2, 1940 2,189,301 Smith Feb. 6,1940 2,370,159 Hanley Feb. 27,1945 

